This invention relates to electromagnets for degaussing, or rendering de-magnetized, record-reproduce heads in tape recorders, e.g.
The record-reproduce head of a tape recorder generally has a propensity for picking up magnetism, that is, becoming magnetized in the course of its service, so that its record-reproduce characteristic deteriorates gradually on account of the unwanted magnetism growing in the head. In order to avoid this deterioration, it is necessary to periodically degauss the head. Such degaussing is conventionally accomplished by using a head-degaussing electromagnet. In one known method, the electromagnet is energized to generate a constant alternating magnetic field. This electromagnet is first located close to the head face, that is, the surface which is in sliding contact with the magnetic tape, and is then moved away from said face. In another known method, the electromagnet is located close to the head face; it is first energized fully to produce a strong alternating magnetic field and is gradually de-energized to atrophy its magnetic field to zero. These methods, however, are accompanied by drawbacks since in tape recorders and similar devices, a tape guide for guiding a running tape in the given path or track of sliding movement along the head face is located in the vicinity of the head. The position of the guide relative to the head is necessarily such that it impedes the degaussing action if the yoke of the electromagnet is sized wider than the tape. On the other hand, if its yoke is sized narrower than the tape, the ends of the track part of the head face receive inadequate degaussing action.
This invention overcomes these drawbacks by providing an electromagnetic as will positively and reliably degauss record-reproduce heads in magnetic tape devices, including tape recorders, already in existence. A yoke face is employed which is wider than the magnetic tape, in the region at and adjacent to the gap, and narrower than the tape in side regions remote from the gap.
Examples of a presently preferred head-degaussing electromagnetic embodying this invention will be described in reference to the attached drawings.